Chapter 4 Flashcards
(36 cards)
What is the term for “normal alleles”
Wild type
They are made in proper amounts and function normally
What does genetic polymorphism do in large populations
Produce more than one wild type
What are mutant alleles
Alleles that have been altered by a mutation
They are usually rare and defective in their ability to express a functional protein
They are also usually inherited recessively
When does the recessive allele not affect the phenotype
In a simple dominant/recessive relationship
What are the two possible explanations that can explain the wild type phenotype of a heterozygote
Half of the normal protein is enough to accomplish the proteins cellular function
The heterozygote may produce more than 50 percent of the functional protein
Why is the normal gene considered to be “upregulated”
It has to compensate for the lack of function of the defective allele
Which genotype is considered the loss of function alleles
The recessive alleles
In the case of purple and white flowers the white flowers have the homozygous recessive genotype which means they have a 0% functional protein
What is a gain of function mutation
The protein encoded by the mutant gene is changed so it gains a new or abnormal function
What is a dominant negative mutation
When a protein encoded by the mutant gene acts antagonistically to the normal protein
What is happloinsufficiency mutation
This mutant is a loss of function
The heterozygote doesn’t make enough product to give the wild type phenotype
What is incomplete penetrance
When a dominant allele doesn’t influence the outcome of a trait in a heterozygote individual
In some cases the individual can carry the dominant allele but they don’t show the trait
What is expressivity
The degree at which a trait is expressed
Usually affects phenotypes in the environment and with other modifier genes
What is incomplete dominance
When a heterozygote exhibits a phenotype that is an intermediate between the homozygotes of that trait
White and red flowers make pink
Why does a trait being dominant or incomplete dominant depend on how close we look at certain genes
Organisms may seem to be expressing dominant traits when they are actually expressing incomplete dominance
A pea may look round but it lacks the amount of starch a homozygous dominant pea has
What is over dominance
When a heterozygote has a greater reproductive success compared to both the homozygotes of that trait
They only have a higher success rate however in environments that allow them to be successful
Heterozygote individuals with sickle cell are only more successful in areas where malaria is high but in other places like the US they are not more successful
What is overdominance caused by
Two alleles that produce slightly different proteins and a favorable phenotype in the heterozygote
What are the three possible explanations for over dominance at a molecular level
Disease resistance
Homodimer formation
Variation in functional activity
Why do homodimers sometimes have more functionality
They have functions from two different dimers giving them functions from both
What is codominance
When both alleles are expressed in a heterozygote
Blood types are a great example of
Why do x linked diseases show affected males with their mothers as carriers
Because males inherit only one X gene so if the mother has the gene then the son will too
What is pseudoautosomal inheritance
Genes found on both the X and Y chromosome
Usually found in homologous regions
What is sex influenced inheritance
Allele is dominant in one sex but recessive in the opposite sex
These traits are autosomal and the individuals are usually heterozygotes
What is sex limited inheritance
Traits that occur in one of two sex
The genes are usually controlled by sex hormones
Ovaries developing in females is a good example
What is a lethal allele
Has the potential to cause death of an organism
Usually inherited in a recessive way and it’s usually the result of a mutation in essential genes
